1. Field of the Invention
The present invention relates to a method and apparatus for moving, filtering and ionizing air. More particularly, the present invention relates to a fan assembly having a tubular housing and electrodes which ionize air and cause the air to be filtered and to move through the tubular housing without use of moving parts, such as an impeller, thereby providing air filtration and ventilation without generation of vibrations and acoustic disturbances.
2. Description of the Related Art
Conventional fans, ventilation systems and air filtration systems presently used in industrial, commercial and residential applications typically employ an impeller or the like to generate an air flow. The rotary movement of the impeller in such systems causes acoustic disturbances and vibrations, the noise level of which may be excessive for a particular application. For example, it may be desirable to generate a virtually noiseless air flow for industrial applications such as cooling of personnel or equipment, exhausting and/or filtering of air, drying processes, and clean room applications. Noiseless air filtration may also be desirable in residential ventilation and filtration systems. Conventional impeller-based devices are incapable of providing air movement without generating significant noise. Accordingly, there is a need for a system capable of providing noisefree air flow and/or air filtration.
Electric fields have been used in a variety of technologies to ionize molecules or to generate a stream of electrons. For example, electrostatic precipitators conventionally use an electrostatic charge to remove particles from an air stream by attracting electrostatically charged particles to an oppositely charged collector. The system disclosed in U.S. Pat. No. 4,518,401 to Pontius et al. is representative of such systems. Specifically, Pontius et al. disclose an electrostatic precipitator comprising a plurality of positively-charged, longitudinally-extending vertical plates and a plurality of negatively-charged, vertically-extending rods interspaced between the plates. As air flows through the precipitator, the electric field formed between the rods and plates causes a corona discharge from the rods which negatively charges particles in the air, which are then drawn to the positively-charged plates and removed from the air. The plates are mechanically rapped periodically, causing the particles to fall into collection hoppers.
Other patents disclosing electrostatic precipitators include: U.S. Pat. No. 2,593,869 to Fruth; U.S. Pat. No.2,756,838 to Roberts; U.S. Pat. No.2,778,443 to Yereance; U.S. Pat. No. 3,798,879 to Schmidt-Burbach et al.; U.S. Pat. No. 3,910,778 to Shahgholi et al.; U.S. Pat. No. 5,199,257 to Colletta et al.; U.K. Patent No. 2,229,117 to Colletta; German Patent No. 4410213 to Kogleschatz; and German Patent No. 4400827 to Pechmann. In each of these systems, the air flow through the precipitator is generated by conventional means, and the electric field within the precipitator is generally perpendicular to the direction of flow; consequently, the ionizing action of the precipitator and the shape and orientation of the electric field are not suitable for causing or increasing air flow.
Electric fields have been used in conjunction with magnetic fields in ion pumps to form a vacuum by ionizing air molecules and causing the ions to colloid with and be buried within a cathode material. For example, U.S. Pat. No. 4,631,002 to Pierini discloses an ion pump comprising hollow anode elements formed between two cathode plates disposed between opposite poles of a magnet. Other patents disclosing ion pumps include U.S. Pat. No. 4,687,417 to Amboss and U.S. Pat. No. 3,452,923 to Lamont. While such pumps ionize air molecules, they are designed to trap such molecules and thus cannot generate an air flow.
Electric fields have also been used in electron beam generators and accelerators to accelerate electrons. For example, U.S. Pat. No. 5,463,268 to Schroeder discloses an electron accelerator which employs a negatively-charged electrode within an acceleration tube and conductive rings to accelerate electrons to a high velocity. U.S. Pat. No. 3,431,455 to Beyer discloses an electron imaging device which directs a beam of electrons onto a surface to form a charge pattern. Such devices typically operate in a vacuum and are not suitable for ionizing and accelerating air molecules or generating an air flow.
While the above patents establish that electric fields have been used to ionize air molecules and particles and to accelerate electrons, electric fields have not been exploited in the generation of an air flow, such as that produced by conventional impeller fans. In particular, it has not been demonstrated that a significant volume of air can be moved through a chamber from an air inlet to an air outlet by applying an electrostatic field to the air within the chamber. Further, conventional electrostatic precipitators used in ventilation systems do not enhance or increase air flow. Thus, fans that employ an electric field as a means of moving air are unknown.